Locking devices for bushings and structures thereof



Se'pt. 30, 1958 R. s. QUIMBY `2,854,503

- LOCKING DEVICES FOR BUSHINGS AND STRUCTURES THEREOF Filed A'pm 1v. 195s /NVENTUR ROBE/2T 5. .QU/MBV www5.

TTC NEV United ttes Patent LOCKING DEVICES FOR BUSHINGS AND STRUCTURES THEREOF Robert S. Quimby, Lexington, Mass., assignor to Raytheon Manufacturing Company, Newton, Mass., a corporation of Delaware Application April 17, 1953, Serial No. 349,439

2 Claims. (Cl. 174-148) This invention relates to a locking device to be used in combination with bushings and to the structure thereof.

One of the problems encountered when bushings are assembled and mounted is the tendency for the terminal stud in the bushings to turn when leads are attached thereto. When the bushings extend into oil-lled cases, such as are often used to house transformer components, this problem is more diicult because the oil lubricates the terminal stud and allows it to turn more easily. The resulting danger involved in regard to such turning is that the internal leads attached to the bushings may be broken off; Also, every variation in the hardness of the compression-type insert provided within such bushings requires a dierent tension on the bushing assembly to tighten it adequately to prevent this turning. How ever, such tightening may distort the insert beyond its useful limits before proper tightness is obtained.

This invention involves the use of a novel locking device which prevents the terminal stud in the bushing from turning and obviates the undesirable conditions described above even when the terminal stud extends into an oil-lled case. The principal component in this device is a rigid bar-like strip or piece which, when xed at one point to the terminal stud of a supported bushing and at another point by any suitable means, will react against a torque applied to the stud to prevent the stud from turning. In practice, the locking device usually bridges two or more terminal studs and is made of rigid nonconductive material to insulate the studs from each other. However, if it is desirable to secure the terminal stud of a single bushing, this may be accomplished by anchoring one end of the strip by suitable means, for example, to the case through which the bushing extends, and the other end may be xed to the terminal stud by using the same components employed to x two or more studs.

This invention and features thereof will be understood more `clearly and fully from the following detailed description of one embodiment of the invention with reference to the accompanying drawing wherein:

Fig. 1 is an enlarged exploded view of a locking device made in accordance with this invention to be used to secure three bushings:

Fig. 2 is a side view of Fig. l taken along line 2*-2;

Fig. 3 is an enlarged view of an assembled locking device made in accordance with this invention; and

Fig. 4 is a bottom view of Fig. 3 taken along line 4-4 with one section of the locking device shown in an unassembled stage.

Referring now to Fig. l, a group of three lead-in bushings 1, 2, and 3 extending into a metal case 4 is shown for the purpose of illustrating this invention. These bushings are of the type described by Richard U. Clark in his United States Patent No. 2,447,489. However, it should be noted that the invention as described herein is not limited in its applicability to the group of bushings shown either as to number or type. The bushings 1, 2, and 3 are of the type commonly used in transformer deice vices where it may be desirable to till the transformer case with oil. In such devices, the bushings are provided with an insert 5; for example, neoprene and silicone inserts have been used for this purpose. These inserts 5 may be compressed about the area where the bushings enter the case 4 to -seal these areas and to prevent oil Within the case from escaping. Thus, it may be seen that the internal extension of the terminal stud 6 on each of the bushings will be lubricated with oil when it is used in conjunction with such oil-filled devices. Ordinarily, the bushing assembly is tightened and sealed by rotating a nut upward on the threaded stud 6 until the insert 5 is compressed against the case and the assembly is unable to turn. However, the tension which is required to achieve the proper tightness is often great enough to distort the insert 5 beyond its useful limits. When the bushing extends into an oil-filled case, the problem of achieving the proper tightness becomes more diicult because of the increased ease with which the lubricated parts may turn. The locking device described below eliminates these difficulties and permanently positions the bushings in relation to the case 4.

Referring now to Figs. l, 2, 3, and v4, the first member of the locking device is a rectangular insulating piece 7 provided with an elongated hole 8 which extends along a major portion of the length of the piece. This piece should be made of an insulating material which has sufficient rigidity and strength to withstand any turning torque which might be ordinarily applied to the bushings. A rectangular glass melamine strip has been used successfully for the purpose of forming the piece. However, it should be noted that the piece 7 need not be made of insulating material if a short circuit between the bushings will not effect the operation of the device in which they are used. The design of the piece 7 may be seen with greater clarity in Fig. 4, and the broken-away section 9 of the piece is illustrated therein to show that insulating material has been used in this particular embodiment of the invention. The piece 7 is designed to permanently position three bushings but a similar piece can be easily made to accommodate more or less. However, as a practical matter, these pieces are ordinarily made for groups of two cr three bushings. Thus, any number of bushings may be properly positioned by using these two sizes in combination. The piece 7 is placed over the terminal studs 6 extending from the bushings 1, 2, and 3. It should be noted that, since the hole 8 is elongated, the spacing between the terminal studs, as shown in Fig. 4, is not critical.

The second member of the locking device is a metal clip 10 having an opening 11 therein. These clips are made with opposing right angle edges, as shown in Fig. 2. The depth of these edges should be approximately equal to the thickness of the insulating piece 7. Thus, the clips lt) may be positioned over the studs 6 so that the edges and the upper faces of the clips overlap the sections of the insulating piece 7 which are adjacent to these studs, as shown in Fig. 3. When the clips 10 are permanently locked on the terminal studs 6, they cooperate with the insulating piece 7 to effectively prevent the studs from turning.

Two other members, a lead lug 12 and a nut 15, are added to the assembly to facilitate the ease with which internal leads may be connected to the bushings and to provide the pressure necessary to properly seal the openings through which these bushings extend. Thus, a lead lug 12, having a large opening 13 through which a stud 6 may extend and a small opening 14 to which a lead may be connected, is placed over each of the terminal studs 6. These lugs 12 may be seen in Figs. l, 2, and 3 but are more clearly pictured in Fig. 4. Likewise, a nut l5 is provided for each of the bushings 1, 2, and

a 3, and is threaded onto the respective terminal studs 6 until the bushings and the inserts are sufficiently compressed to seal the openings in the case 4 through which these bushings project. When the inserts 5 are properly compressed, the lugs 12, the nuts 15, and the clips 111 may be soldered to the terminal studs 6, thereby permanently locking these studs so that they are unable to turn.

However, this invention should not be limited to the particular details described above as many equivalents will suggest themselves to those skilled in the art. For example, the clips 18 could be made with only one rightangle edge. Likewise, the lead lugs 12 could be eliminated entirely and the internal leads could be connected directly to the terminal studs 6. Also, lead lugs having one right-angle edge could be designed, thereby combining the individual features of a lead lug 12 and a clip 19 in one component. Furthermore, any rigid material having good insulating qualities may be used to form the insulating piece 7, and this piece could be fixed at one end so that a single bushing could be locked in position. In addition, the locking device may be used on other bushings and is not limited to the compression-type leadin bushings shown. Therefore, it is desired that the appended claims be given a broad interpretation commensurate with the scope of the invention Within the art.

What is claimed is:

l. A bushing anti-rotational locking device comprising in combination an insulating bushing having a substantially circular cross section, an apertured member, a conducting terminal stud extending through said bushing and said member and being insulated from said member by said bushing, an anti-rotational locking structure comprising insulating material having an elongated 4 I hole along the major portion thereof through Which said stud extends and a structure immovably xed to said stud and bearing on an outside edge of said anti-rotational locking structure whereby rotation of said stud with respect to said locking structure is prevented.

2. A bushing anti-rotational locking device comprising in combination a plurality of insulating bushings, an apertured member, conducting terminal studs extending through said bushings and said apertured member and being insulated from said member by said bushings, an anti-rotational locking structure comprising a strip hav ing an elongated hole along the major portion thereof through which said studs extend, said anti-rotational locking structure being removed from Contact with said apertured member and being in pressure engagement with said bushings, and a structure immovably xed to said studs and bearing on an outside edge of said antirotational locking structure whereby rotation of said studs with respect to said locking structure is prevented.

References Cited in the tile of this patent UNITED STATES PATENTS 1,749,359 Smalley Mar. 4, 1930 2,286,755 Morton June 16, 1942 2,286,829 Reid June 16, 1942 2,461,487 Wagsta Feb. 8, 1949 2,514,440 Breisch July 11, 1950 2,554,078 Werner May 22, 1951 2,659,766 Fot Nov. 17, 1953 FOREIGN PATENTS 284,976 Italy Apr. 28, 1931 

